Vaccine preservative: no brain damage

For at least 20 years there have been arguments about the alleged brain-damaging effects of a mercury-based preservative in vaccines, called thiomersal.

The idea was put about that thiomersal vaccines caused autism, and vaccine manufacturers have been progressively replacing thiomersal.

In the early days of the controversy there was a panic and some children died because they didn't receive their immunisations on time. A couple of years ago a boy with autism died because he was given a dangerous chelating agent under the misguided notion that he needed to have mercury removed from his body.

But there's very little evidence of brain damage and that's been confirmed in a well designed large study in 7- to 10-year-olds, which compared early thiomersal exposure to a list of 42 measures of brain and nervous system development.

The researchers found no significant links with damage. In fact some of the time there were indications of improved brain function in children exposed to thiomersal. This paper supports findings from the UK about three years ago showing similar findings.

So while it's a sensible precaution to remove thiomersal from vaccines, the study provides reassurance to parents that no measurable harm has been done to children who've received it.